Top one is oil level.----Next one down ( do not remove ) is a lock screw for pinion bearing.----Next one down ( do not remove ) is pivot screw for shifter fork.----Bottom screw is drain and FILL screw.------Simple job that can lead to EXPENSIVE mistake!
If you want this motor to last another 50 years , it needs a new impeller.----Seal kit as well , if never done.-----First take it apart for inspection BEFORE ordering parts.
Any water in the gearcase oil ?----Those lower units can not tolerate water.----Damages the driveshaft and bushing above the pinion gear.-----Some gas / oil mix goes right through the motor and ends up with what you see.-----I recommend a lower unit seal kit if it was never done yet.----Shift...
Look into fitting a manual primer valve,----Used on many Johnson / Evinrude models.-----Bypasses the choke set up;----Keep looking for a blown up donor motor.---$500 or less.-----Your location?-----Motor serial #?